1. Field of the Invention
The present invention relates to a method and system for controlling a location update of a Mobile Station (MS) and paging the MStaking into account location characteristics of the MS in a Broadband Wireless Access (BWA) communication system.
2. Description of the Related Art
Most wireless networks including a BWA network support handover for an MS. To efficiently support the handover, it is preferred to reduce handover-caused system load and power consumption of the MS and to shorten a time delay involved in completing the handover process.
Handovers over a wireless network can be categorized into an active-mode handover, for an MS that operates in the active mode, and an idle-mode handover, for an MS that operates in the idle mode.
If an update condition is met, the MS that performed the idle handover performs a location update by registering its location with a paging controller via a Base Station (BS). The paging controller is a network entity that manages idle-mode MSs. The Institute of Electrical and Electronics Engineers (IEEE) 802.16e standard defines four location update conditions, which will be taken as an example herein. The four location update conditions include a paging group update, a timer update (periodic time), a power-down update and a Media Access Control (MAC) hash skip threshold update.
The MS updates its location according to the four location update conditions, as follows.
In the paging group update, the MS receives a broadcast paging group Identifier (ID) from a preferred BS during a Paging Listening Interval (PLI) that was negotiated preliminarily with the network and determines whether the paging group ID is identical to a last paging group ID that the MS is aware of. The paging group ID is set in a Downlink Channel Descriptor (DCD) or a Mobile_Paging-Advertisement (MOB_PAG-ADV) message. Upon detection of a change in the paging group ID, the MS performs location update. The preferred BS is a BS that the MS synchronizes its timing to during the PLI. The DCD is a broadcasting message including information required for the MS to receive a downlink message and downlink traffic from the preferred BS. The MOB_PAG-ADV message is a broadcasting message including information indicating whether an incoming signal has been generated for an MS registered to a paging group of the preferred BS and the ID of the paging group. The paging group includes BSs that cover areas in which the MS can receive the MOB_PAG-ADV message indicating generation of an incoming signal for the MS. One BS can belong to one or more paging groups.
In the timer update, the MS is equipped with an idle mode timer. Before expiration of the idle mode timer, the MS performs location update.
In the power-down update, the MS notifies the paging controller managing the MS of its power-down as a power-down procedure. Then the paging controller does not manage information regarding the MS any longer by deleting the information regarding the MS. The power-down refers to reduction of power consumption in time periods other than the PLI in the idle-mode MS. The power consumption occurs during an unavailable paging interval.
In the MAC hash skip threshold update, the MS performs location update, if the count of the MS managed MAC hash skip counter exceeds a MAC hash skip threshold. The MAC hash skip threshold is acquired from a Deregistration Command (DREG-CMD) message that the MS should receive from the preferred BS to enter the idle mode during initial ranging. When the location update is successful, the BS and the MS initialize their MAC hash skip counters. The DREG-CMD message is a message used for the BS to command the MS to change its operation mode to the idle mode. The MAC hash skip threshold defines a maximum number of successively received MOB_PAG-ADV messages that do not have MAC address hashes.
An MS located in a cell having obvious mobility characteristics, such as a cell under a company-like or building-like indoor environment, has inertia in mobility. The inertia affects the update location operation of the MS. For example, when the MS moves into a building, its mobility is substantially low. That is, when a user works at his workstation or participates in a meeting, the mobility of his MS is almost zero. Nonetheless, an unnecessary location update takes place conventionally.
When the user's continuous movement in an elevator of a building is not fast for a certain time period, the MS performs frequent location updates due to a bad channel environment.
The conventional location update operation does not reflect the location characteristics of the MS. Therefore, signaling overhead increases during location updates between the BS and the MS.
Therefore, a need exists for a system and method for delaying a location update of a Mobile Station (MS) and paging the MS.